Believe it or not, notaries are the oldest branch of the legal profession and, in the UK, we're mainly used to authenticate documents for use overseas. This can be for a variety of reasons, such as proving the identity of an individual or company, confirming the validity of documents or confirmation that an event has happened.
Usually, the person or company you are dealing with overseas will tell you that a document needs to be notarised. Occasionally you may use a notary for documents in the UK, possibly for an ID1 to prove your identity to a solicitor in the UK.
Solicitors may offer to countersign or authenticate your signature, but the document will possibly be rejected, and you will need to see a notary anyway. This will cause extra costs and delays.
Some documents don't actually need to be notarised. This can be because they have been issued by a government body and have a wet signature attached, or because the receiving country deems them to be acceptable as they are due to their nature.
Most documents have to be in an original format to be acceptable, there are a few exceptions to this, but copies of documents are limited and should be notarised. Some documents cannot be copies at all, such as birth, marriage or death certificates, DBS certificates. This is due to crown copyright, anything that that has this attached, means it cannot be copied.
Sometimes, in addition to notarisation some countries also ask for an apostille, which confirms the signatory on the document. This is done by the Foreign, Commonwealth and Development Office.
Sometimes, however, in addition to this you might also be asked to obtain legalisation. This in turn confirms the apostille.
If you need assistance with your documents, please do not hesitate to contact me.